001/*
002 * Copyright (C) 2007 The Guava Authors
003 *
004 * Licensed under the Apache License, Version 2.0 (the "License"); you may not use this file except
005 * in compliance with the License. You may obtain a copy of the License at
006 *
007 * http://www.apache.org/licenses/LICENSE-2.0
008 *
009 * Unless required by applicable law or agreed to in writing, software distributed under the License
010 * is distributed on an "AS IS" BASIS, WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express
011 * or implied. See the License for the specific language governing permissions and limitations under
012 * the License.
013 */
014
015package com.google.common.base;
016
017import com.google.common.annotations.GwtIncompatible;
018import java.lang.ref.ReferenceQueue;
019import java.lang.ref.WeakReference;
020
021/**
022 * Weak reference with a {@code finalizeReferent()} method which a background thread invokes after
023 * the garbage collector reclaims the referent. This is a simpler alternative to using a {@link
024 * ReferenceQueue}.
025 *
026 * @author Bob Lee
027 * @since 2.0
028 */
029@GwtIncompatible
030public abstract class FinalizableWeakReference<T> extends WeakReference<T>
031    implements FinalizableReference {
032  /**
033   * Constructs a new finalizable weak reference.
034   *
035   * @param referent to weakly reference
036   * @param queue that should finalize the referent
037   */
038  protected FinalizableWeakReference(T referent, FinalizableReferenceQueue queue) {
039    super(referent, queue.queue);
040    queue.cleanUp();
041  }
042}